This error message occurs because the Exchange Server 2007 server uses adomain\username format during connectivity tests for standard authentication methods. However, in a disjoint namespace scenario, the domain name of the Exchange Server 2007 server differs from the domain name of the Active Directory.

There are three articles of similar symptoms that were released. The following Microsoft Knowledge KB articles describe different authentication methods scenarios and different disjoint namespace scenarios problems:

You still receive unexpected error messages when you run the Test-OwaConnectivity command or the Test-ActiveSyncConnectivity command after you apply hotfix KB954213 on an Exchange 2007 Service Pack 1-based server

Note Update Rollup 2 for Exchange Server 2007 Service Pack 2 resolves the issues in these three articles in addition to the issue that is described in this article.

For more information about disjoint namespace scenario, visit the following Microsoft Web site: